Block copolymers comprising 2 or more types of polymer segment are known to form microphase-separated structures with a molecular length of about several nm to several hundreds of nm, when the affinity between segments is low. Microphase-separated structures generally vary depending on the copolymerization ratio of one segment to the other segment. Diblock copolymers comprising two polymer segments form phase-separated structures such as spherical, tubular (cylinder), bicontinuous (gyroid), or layered (lamellar) structures, with the increase of the proportion accounted for by either one of the two segments. When the proportion accounted for by a segment exceeds one half thereof, reverse phase structures are formed.
Various applications of such microphase-separated structures have been examined regarding nanoscale templates. For example, cylindrical structures are formed and a cylinder is filled with a magnetic recording medium, so that a nanoscale patterned magnetic recording medium can be prepared (Patent Document 1). Moreover, microphase-separated structures have been applied to various industrial fields, such as a nanowire template (Patent Document 2), a highly efficient light emitting device (Patent Document 3), and mirror for laser oscillation (Non-Patent Document 3).
The formation of uniform and stable phase-separated structures is important for these applications. A block copolymer solid is generally produced by a solution-cast method or the like, but no clear phase-separated structure is formed by the method alone. This is because entangled polymers are frozen upon solid formation. Therefore, a technique is employed for the development of various applications, which comprises heating once to the glass transition point (Tg) or higher, gradually cooling, and thus forming clear and uniform phase-separated structures (Non-Patent Document 1). This technique is employed for increasing the motility of macromolecular chains so as to further increase the interaction between polymer chains. However, this technique requires to maintain a block copolymer solid for several days to several weeks while heating it at Tg or higher, resulting in very low productivity and a barrier against practical application. This is because macromolecular chains generally require a long relaxation time, taking a long time for structural transition.
Meanwhile, Russell et al. have reported that a film with high uniformity can be obtained by exposing a block copolymer solid to solvent vapor having affinity for one or both segments of each block copolymer (Non-patent document 2). However, this technique is also problematic in that it takes much time, such as about several days, and the technique can be applied to only a thin film with a thickness that allows a solvent to permeate it.
Similar problems are present for also alloys, blends and composites for which block copolymers are used. The terms alloys, blends and composites refer to those prepared by mixing compatible polymers, those prepared by mixing incompatible polymers, and those prepared by combining at least one type of polymer with a heterologous material, respectively (Non-Patent Document 3).
[Prior Art Documents]
[Patent Documents]
    [Patent Document 1] Yoshiyuki Nagataki, Shoji Nishihara, Ichiji Miyata, Kenji Kono, “Magnetic Recording Medium,” JP Patent Publication (Kokai) No. 5-298666 A (1993)    [Patent Document 2] Tuominen Mark, Russell Thomas P, Ursache Andrei, and Bal Mustafa, “Nanofabrication,” JP Patent Publication (Kohyo) No. 2004-527905 A    [Patent Document 3] Fong Hon Hang, Kiyotaka Mori, George G Malliaras, Yu Jye Foo, “Electroluminescent Device Designed So As To Have Mobility,” JP Patent Publication (Kokai) No. 2008-131029 A[Non-Patent Documents]    [Non-Patent Document 1] Sang-Min Park, Gordon S. W. Craig, Young-Hye La, and Paul F. Nealey, Macromolecules, 2008, 41, 9124-9129    [Non-Patent Document 2] Kevin A. Cavicchi, Keith J. Berthiaume, Thomas P. Russell, Polymer 46, 2005, 11635-11639    [Non-Patent Document 3] “Polymer ABC Handbook” Edited by Research Group on Polymer ABC, The Society of Polymer Science, Japan, NTS Inc.